Sound amplifier



Jam. i4, Q., Q 1H, LARSSQN KL SOUND AMPLIFIER' Filed Feb. 24, 1928 3 Sheets-Sheva l C. H. LARSSQN SOUND AMPLIFIER Filed Feb. v24, 1,928 5 Sheets-Shee''.

Jan. 14, 1930)` c, H, LARSSON 1,743,784

SOUND AMPLIFIER Filed Feb. 24l 1928 3 Sheets-,Sheet 5 Patented `ian. 14, 1930 CARL H. LARSSON, OF CHICAGO, ILLINOIS SOUND AMLIFIER Application filed February 24, 1928. Serial No. 256,535.

j This invention relates to sound amplifying apparatus which may be adapted for various purposes but which is particularly intended for use in connection with phonographs or radio receiving apparatus.

The desirability of having some form of amplifier which will provide true sound or tone amplification has been long recognized but has been found exceedingly difficult to accomplish. The present invention is intended to provide sound or tone amplification which will be truc and correct to the j fullest degree possible whereby all of the sound vibrations within the audible range will be amplified and projected with as little distortion as possible so as to give most satisfactory and pleasing results.

Among the further objects of this invention are toprovide a sound amplifier which is particularly adapted for use in connection with phonographs or as a radio loud speaker; to provide a sound amplifier of a combined horn and reflector type; to provide a device of the character set forth having one or more projecting surfaces and means to carry the sound from the place ofproduction and directing it onto such surface or surfaces which in turn project it toward the hcarer; to provide a device of the character set forth having a receiving throat which connects with a bifurcated horn or sound passageways having their outletsdirected toward a reflecting surface or surfaces; and to provide such other advantages and novel features as will be described more fully hereinafter.

In the accompanying drawings illustrating this invention;

Figure 1 is a front viewof my improved device or amplifier shown in cabinet form;

Figure 2 is a cross sectional view taken on the line 2-2 of Figure '3; and

Figure 3 is a vertical sectional view taken on the line 3 3 of Figure 2; and

Figure 4 is a vertical sectional view taken on the line 44` of Figure 3.

In the particular form of the device as shown in these drawings, the parts ,are mounted in a cabinet or box 6 which may be made in any desired form and which may serve t0 enclose the phonograph reproducerJ mechanism or parts of a radio receiving apparatus if desired. The amplifier has an inlet throat or column 7 which passes through a hole in the top 8 of the cabinet and which 1s adapted to receive or be connected with 55 the tone arm of a phonograph or a radio reproducer element. The throat 7 leads to a bifurcated passageway comprising horns or branches 8 and 9 which extend outwardly. toward the sides 10 of the cabinet an-d down- 60 wardly, Aas shown particularly in- Figure 3. iVhen the throat is positioned adjacent to the back 11 of the cabinet as shown in Figure 4, these branches or horns also bend or turn forwardly toward their lower ends to a considerable degree. While 'the throat 7 is preferably round, the branches or horns 8 and 9 are preferably rectangular in cross section and gradually kincrease in size toward their lower ends where they are connected respectively with downwardly extending projections or extensions 12 and 13 which are curved or arranged so as to bring their mouths toward the bach/of the cabinet and which haved substantially lateral or side outlet openings 14 and 15. The sound passageways or horns lead into a somewhat peculiarly shaped outlet or outlet chamber which opens toward the front of the cabinet and extends through the front wail 16 thereof, as shown particu- 80 larly in Figure 3; the sides 17 and 18 of this outlet chamber are preferably arranged so that they converge toward the back lof the cabinet.

The bottom of the chamber is formed by the bottom 19 of the cabinet. The top coinprises an arch or 'domer 20 which is also arranged at an angle, as shown in Figure 4, so that there is a general enlargement ofthe chamber from the back toward the front. The back 21 of the outlet chamber which preferably comprises a sounding board is provided with two forwardly facing vertically extending deflecting surfaces or faces 22 and 23 which unite in a central vertical rib 95 or edge 24. These surfaces are in the main A approximatelyin the form of quarters of cylindcrs but unite or coalesce with somewhat similarly shaped defiecting surfaces in the corner blocks or side resonators 25 and 2G 10C at the mouths of. hehorns to form substant tially semi-circluliaL `,-cdeflecting surfaces, as shown particularly in Figure 2.

The upper portion-of the back is also curved forwardly, as shown at 27, where it unites with the dome or arch 20 and isfcurved forwardly, as shown at 28, where it unites with the bottom 19.V rlhis arrangement of the back and outlet chamber asfa whole is such as to project the sound/'or tone forwardly in the most natural mar/ther. i' The outlet .chamber is preferably provided with doors 29 at the front whichy mayfserve to protect the inner parts and may also serve as valves'for controllingthe tones from the amplifier. A screen or grill 30 is also preferably arranged at the front of the outlet chamber which may serve not'only for ornamental` purposes and concealing or protecting the inner parts but also for the purpose of softening the tones if desired.

l/Vhile any suitable material or materials may be utilized forlmaking my improved sound amplifier or 'loudgspeak'er device, I have found that particularly. -good results may be obtained by making the entire device of wood. The horns or conducting passageways from the throat to the outlet or resonant chamber are preferably made of sufliciently thin wood so that the Walls thereof will be resonant while the back 2l of the outlet or resonant chamber may be formed of a thicker board or boards, forinstance in the ones constructed this back or sounding board is approXimately one-half inch in thickness.

`When a sound or tone is directed into the throat or opening 7, it passes `downwardly' and is divided on the relatively sharp edge or' projection between the horns, a portion of the sound passing downwardly through each horn where it is amplified and eventually passes out through the openings 14 and 15 into the central outlet or resonant chamber.

e As the sound passes out through these openserves in the nature of a sound post for the dome or top sound board'20. It willalso be noted that the shape of the back, as well as the top, bottom and sides of the outlet or resonant chamber is such that the sound or tones will tend to be thrown forwardly from all positions.

I have found from actual use that this construction is such that reproductions made by phonographs as well as the output of radio receiving elements will be ampliiied so that the entire range of audible vibrations, as produced by various musical instruments as well as by the voice will have their natural and proper tones without distortion.

It will be noted that various changes may weave-i be made in thebdet ls/,efxconstruction and arrangement of th parts, as well as in the variety of the materialsuse'd for constructing the amplifier without departing from the aim and purpose of this invention; therefore l do not wish to be limited to the exact details herein shown and described, except as specified in the following claims, in which l claim:

l. A soundV amplifier comprising an inlet throat, two tortuous passageway-'s leading downwardly from said throat, an outlet chamber positioned between said passageways and spaced therefrom and having a back with vertically arranged concave detlecting surfaces at either side thereof, said passageways having openings into said chamber which are directed toward said de-` flecting surfaces.

2. In a device of the character set forth, the combination of a resonant chamber having diverging lateral walls and having a. back with a central vertical vforwardly extending projection with curvedides, a pair of horns having outlet openings in the sides of thel chamber, said horns being mounted at the sides of the chamber and spaced therefrom and being united in a common inlet pipe.

3. In a device of the character set forth, the combination of a cabinet, an amplifying chamber in said cabinet having an opening through the front wall of the cabinet and having a sound deilecting rear surface, an inlet throat arranged above said chamber, and passageways leading from the throat downwardly and over the sides of the recess and having outlet openings into the sides of the chamber.

il. Thecombination with a cabinet, of an outlet or resonant chamber open to the front of the cabinet, doors for closing saidopening, said chamber having a rear wall with a central vertical projection provided with cncave sides, a sound receiving inlet at thel top of the cabinet, passageways leading from said inlet over the sides of the chamber and downwardly and spaced from the chamber and cabinet, said passageways increasing in area from the inlets to their outlets which outlets open into the sides of the chamber, said passageways having curved walls adjacent to the outlets for directing the sound laterally into the chamber and against the sides of said projection.

5. A device of the character set forth, comprising an outlet chamber having an open front with diverging side walls, and an arched top wall, the back of the chamber having verti ally-arranged curved surfaces meeting on a median ,line and forming a projection at the center of the chamber, means for closing the open front of the chamber, passageways leading from the sides of the chamber forwardly, then up and rearwardly and inwardly and uniting in a common inlet. said passageways being free from the chamber throughout their entire length, except at the points where they connect therewith, substantially as described.

(i. In a sound amplifier, the combination of a sound board, a resonance chamber open- Aing outwardly from the sound board, a pluing horns leading from a common inlet and having their large ends directed toward the sound board, a chamber arranged between' the horns which is spaced therefrom and facing outwardly, said horns having openings into the sides of said chamber, and deflectors which are curved i'n both vertical and hori- Zontal planes coacting with the sound board and adapted to direct the sound from the two horns outwardly through the outlet passageway in substantially parallel lines.

8. A sound amplifier, comprising a cabinet having a sound board mounted in the back thereof, two sound horns. leading from the top of the cabinet and having their ends directed toward the sound board and having openings in the sides thereof which lead into the resonancev chamber, a resonance' chamber arranged between the horns and opening toward the front of the cabinet, said chamber being separated from the horns, and curved resonators secured to the sound board and adapted to guide the sound from the horns and sound board forwardly through the resonance chamber. -V

9. An acoustical amplifier comprising a cabinet with an amplifying chamber Vwith its side walls spaced from the side walls of the cabinet, means forming a divided sound inlet with amplifying horns 4extending therefrom at the sides of the cabinet between the outer side walls and the amplifying chamber and out of contact therewith, and means forming curved connecting passageways between each horn and the rear of the amplifying chamber.

l0. An acoustical amplifier comprising a cabinet with a central amplifying chamber opening forwardly and having its side and top walls spaced from the walls of the cabinet,l horns leading from the vtop of the cabinet to the sides of the amplifying chamberand t out of contact with the walls of the'cabinet and amplifying chamber, and means including a central resonator forming a continuous guide for sound waves from the horns to the amplifying chamber for merging the sound waves in the same direction of amplification through said chamber.

1l. A sound amplifier comprising a cabinet with a central amplifying chamber having its side walls spaced from the side walls of the cabinet to form spaces, two amplifying horns arranged in said spaces one on either side of the cabinet, said horns having their ends directed toward the back of the cabinet, and passageways from the horns into the amplifying chamber.

l2. A device as per claim 6, having a sound board mounted at the back of the cabinet and having two curved side resonators, and a central resonator which is curved on either side in a horizontal plane and which is curved at the top and bottom in a vertical plane, said resonators forming the rear portions of the passageways from the horns to the amplifying chamber.

13. A sound amplifier having a resonance chamber provided with an arched top and having a central-resonator with concave sides and forwardly curved upper and lower ends in the back thereof, said top being secured to the upper end of the resonator, and lsaid resonator being arched at its upper end to correspond with the arch of the top.

lfl. A sound amplifier comprising an outlet chamber having a sound board at the back thereof and open at the front and having a pluralityof horns leading from a common inlet and lopening into the sides of the chamber, said horns heilig spaced from .the cha'mber and said chamber having nov obstructions therein or in the outlet thereof.

CARL H. LARSSON. 

